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10-23-2015, 02:10 PM   #1
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What is the R for?

TOKINA SD 70-210MM F4-5.6 MACRO ZOOM

I was looking at the above lens in the reviews and noticed an R on the zoom markings.
What is the R for?
Ken

10-23-2015, 02:25 PM   #2
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Hummmm...no idea.
10-23-2015, 02:27 PM   #3
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The red R? Infrared mark -- used to be on lenses with the distance scale.

Chapter 2 - Basic Theory - Infrared focus marks on lenses - LifePixel Digital Infrared Photography IR Conversion
10-23-2015, 06:34 PM   #4
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R is for Infrared

Yes, the R is in the index if you were to shoot true infrared film. Our eyes can only focus using light in the visible spectrum, so if you were shooting infrared film, you manually focus as usual, but then would move the hyperfocal distance or what you were focused on to the R index mark on the lens.

When I last shot infrared, however, the effective ISO is extremely low (less than ISO 25) and using a very dark red filter intended for infrared renders the viewfinder so dark, you can barely see anything. So you're really using a measuring tape or estimating distances. Ilford's SFX200 ISO film is greatly biased toward the red end of the spectrum and simulates b&w infrared but without the great inconvenience of low ISO and heat sensitive media...while giving you very similar results as true infrared.

10-24-2015, 03:04 AM   #5
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The ultimate point, hope and shoot.
Thanks for the replies.
Ken
10-24-2015, 05:13 AM   #6
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You can focus without the filter, adjust the focus point indicated on the lens tho the infrared offset and then put the filter back on.
10-24-2015, 12:57 PM   #7
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Have a look at posting #5 of
https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/283311-m...ml#post3087407

This also links to another source of information.
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